Note: Descriptions are shown in the official language in which they were submitted.
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Description
Glass ceraniic mass and use thereof
The invention relates to a glass ceramic mass, comprising at least one oxide
ceramic, containing barium, titanium
and at least one rare earth metal Rek and at least one glass material,
containing at least one oxide with boron. In
addition, the invention relates to a glass ceramic mass, comprising at least
one oxide ceramic, containing barium,
titanium and at least one rare earth metal Rek and at least one glass
material, containing at least one oxide with
boron and at least one oxide with at least one tetravalent metal Me4+. In
addition to the glass ceramic masses, a use
of the glass ceramic masses is described.
The aforementioned glass ceramic masses are known from US 5 264 403. The oxide
ceramic for the glass ceramic
niass is manufactured from barium oxide (BaO), titanium dioxide (TiOZ), a
trioxide of a rare earth metal (Rek203)
and possibly bismuth trioxide (Bi203). The rare earth metal Rek is for example
neodymium. The oxide ceramic for
the aforementioned compound is referred to as microwave ceraniic since its
dielectric material properties
permittivity (c,), quality (Q) and temperature coefficient of frequency (Tf
value) are very well suited for use in
microwave technology. The glass material in the glass ceramic mass consists of
boron trioxide (B203), silicon
dioxide (SiO2) and zinc oxide (40). A ceramic proportion of the oxide ceramic
in the glass ceramic mass is for
exaniple 90% and a glass proportion of the glass material 10%. A compression
of the glass ceramic mass occurs at
a sintering temperature of about 950 C.
A glass ceraniic mass is known from JP 08 073 239 A which consists primarily
of a glass proportion of a glass
material. The glass material exhibits differing combinations of silicon
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dioxide, lanthanum trioxide (Ln203), titanium dioxide, an alkaline earth metal
oxide and zirconium dioxide (ZrOZ).
Both glass ceramic masses are suitable for use in LTCC (low temperature
cofired ceramics) technology. The LTCC
technology is described for example in D. L. Wilcox et al, Proc. 1997 ISAM,
Philadelphia, pp. 17 to 23. The LTCC
technology is a ceramic multilayer method in which a passive electrical
component can be integrated in the volume
of a ceramic multilayer body. The passive electrical component is for example
an electrical conductor track, a coil,
an induction or a capacitor. Integration is achieved, for exaniple, by
printing a metal structure corresponding to the
component on one or more ceramic film blanks, stacking the printed ceramic
film blanks above one another to form
a composite and sintering the composite. Since ceramic film blanks are used
with a low sintering glass ceramic
mass, electrically highly conductive elementary metal MeO with a low melting
point such as silver or copper can be
sintered in a composite with the ceramic film blank.
An LTCC method is known from WO 00/04577 in which in order to avoid a lateral
shrinkage (zero xy shrinkage)
during the sintering process the composite is constructed from ceramic film
blanks using a first and at least one
further glass ceramic mass. The first glass ceramic mass and the further glass
ceramic mass compress at different
temperatures. The composite is sintered in a two-stage sintering process. The
first glass ceramic mass compresses at
a lower temperature (e.g. 750 C). The non-compressing further glass ceramic
mass suppresses the lateral shrinkage
of the compressing first glass ceramic mass. When compression of the first
glass ceramic mass is completed, the
further glass ceramic mass is compressed at a higher temperature (e.g. 900 C).
The already compressed first glass
ceramic mass now prevents the lateral shrinkage of the further
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glass ceramic mass compressing at the higher temperature. The first glass
ceramic mass compressing at the lower
temperature consists primarily of a glass proportion with a glass material
which contains barium, aluminum and
silicon (barium-aluminum-silicate glass). The further glass ceramic mass
compressing at the higher temperature
consists primarily of an oxide ceramic of the formal compound
Ba6_,,Reka+2XTi18O54 (0 < x< 1), where Rek is one of
the rare earth metals lanthanum, neodymium or samarium. The ceramic multilayer
body obtained as a result of the
two-stage sintering process is characterized by a lateral shrinkage (lateral
displacement) of < 2%.
In the case of a glass ceramic mass having a high proportion of ceramic in the
oxide ceramic, conipression of the
glass ceramic mass takes places primarily as a result of reactive liquid phase
sintering. During the compression
(sintering) process, a liquid glass phase (glass melt) is formed from the
glass material. At a higher temperature the
oxide ceramic dissolves in the glass melt until a saturation concentration is
reached and a separation of the oxide
ceramic occurs once again. As a result of the oxide ceramic dissolving and
separating out again, the composition of
the oxide ceramic and thus also the coniposition of the glass phase or the
glass material can change. For example,
one constituent of the oxide ceramic remains in the glass phase after cooling
of the glass ceramic mass.
On the other hand, in the case of glass ceramic masses having a relatively
high proportion of glass, conmpression
takes places primarily as a result of a viscous flow of the glass melt of the
glass material in the range of a softening
point TOft of the glass material. In this situation, vitrification takes place
below 900 C. The higher the proportion of
glass in the glass ceramic mass, the lower the temperature at which the glass
ceramic mass compresses. However,
the higher the proportion of glass, the lower is the permittivity of the glass
ceramic mass. As the
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proportion of glass increases, the quality and the Tf value of the glass
ceramic mass are also influenced in such a
way that the glass ceraniic mass is no longer suitable, for example, for use
in microwave technology applications.
The object of the present invention is to specify a glass ceramic mass which
compresses at a temperature below
850 C and is nevertheless suitable for use in microwave technology.
This object is achieved by specifying a glass ceramic mass comprising at least
one oxide ceramic, containing
barium, titanium and at least one rare earth metal Rek and at least one glass
material, containing at least one oxide
with boron and at least one oxide with at least one tetravalent metal Me4+.
The glass ceraniic mass is characterized
by the fact that the glass material contains at least one oxide with at least
one rare earth metal Reg. In this situation,
in particular, the glass material contains at least one oxide with at least
one pentavalent metal Me5+.
This object is also achieved by specifying a glass ceramic mass comprising at
least one oxide ceramic, containing
barium, titanium and at least one rare earth metal Rek and at least one glass
material, containing at least one oxide
with boron. This glass ceramic mass is characterized by the fact that the
glass material contains at least one oxide
with at least one pentavalent metal Me5+ and at least one oxide with at least
one rare earth metal Reg. In this
situation, in particular, the glass material contains at least one oxide with
at least one tetravalent metal Me4+.
The glass ceramic mass is a glass ceramic compound and is independent of its
state. The glass ceramic mass can
exist as a ceramic green body. With regard to a green body, a fihn blank for
example, a powder of the oxide
ceramic and a powder of the glass material can be combined
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with one another by means of an organic binding agent. It is also conceivable
that the glass ceramic mass exists as a
powder niixture of the oxide ceramic and the glass material. Furthermore, the
glass ceramic mass can exist as a
sintered ceramic body. For example, a ceramic multilayer body produced in a
sintering process consists of the glass
ceramic mass. This ceramic multilayer body can be subniitted to a further
sintering process or firing process at a
5 higher firing temperature.
The oxide ceramic can be present as a single phase. However, it can also
consist of a plurality of phases. It is
conceivable, for example, for the oxide ceramic to consist of phases each
having a differing composition. The oxide
ceramic is thus a mixture of different oxide ceramics. It is also conceivable
for one or more parent compounds of an
oxide ceramic to be present which are then converted to form the actual oxide
ceramic only during the sintering
process.
The glass material can likewise be a single phase. For example, the phase is a
glass melt consisting of boron
trioxide, titanium dioxide and lanthanum trioxide. It is also conceivable for
the glass material to consist of a
plurality of phases. For example, the glass material consists of a powder
mixture of the specified oxides. A joint
glass melt is formed from the oxides during the sintering process. A softening
point for the glass material is
preferably below 800 C in order to allow the viscous flow at as low a
temperature as possible. In particular, it is
also conceivable for the glass material to exhibit a crystalline phase. The
crystalline phase is formed, for example,
by a crystallization product of the glass melt. This means that the glass
material is present not only as a glass phase
after the sintering process but also in a crystalline form. A crystallization
product of this type is lanthanum borate
(LaBO3), for example. In particular, it is also
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conceivable for the crystallization product or another crystalline component
to be added to the glass material prior
to the sintering process. The crystallization product and the crystalline
component can be used as crystallization
seeds.
The conmposition of the glass ceramic mass is preferably chosen such that the
compression occurs by viscous flow
as a matter of priority. As a result of viscous flow, compression occurs at a
relatively low temperature. A viscosity
temperature characteristic crucial to the compression process, which is
expressed for example in the glass transition
point Tg and in the softening point T~ft of the glass material, can be set for
example by means of a ratio of the
boron trioxide to the oxide of the tetravalent metal Me4+ or to the oxide of
the pentavalent metal Me5+.
At the same time, ahnost independently of the compression teniperature, the
dielectric material properties of the
glass ceramic mass can be varied. Principally as a result of the oxide of the
rare earth metal, it is possible to
harmonize the dielectric material properties of the glass material with the
dielectric material properties of the oxide
ceramic. The greater the proportion of lanthanum trioxide in the glass
material for example, the higher is the
permittivity of the glass material. Moreover, the composition of the oxide
ceramic and the composition of the glass
material are chosen such that crystallization products are formed during
compression (by means of liquid phase
sintering for example) and in particular after compression (at higher
temperatures). These crystallization products
have an advantageous effect on the dielectric material properties of the glass
ceramic mass, such that the glass
ceramic mass can be used in microwave technology. In this manner, it is
possible for example to obtain a glass
ceramic mass with a relatively high permittivity of over 15 and with a quality
of over 350 at a low compression
temperature.
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In a special embodiment the oxide ceraniic has a formal composition
BaRekZTi4O12. The rare earth metal Rek is
lanthanum, for example. The oxide ceramic having this composition is
particularly well suited as a microwave
ceraniic. The Tf value of the oxide ceramic lies in the range between - 20
ppm/K and + 200 ppm/K. By means of a
suitable composition and combination of oxide ceramic and glass material it is
possible to obtain a low absolute Tf
value. If the Tf value of the glass ceramic mass serving as the basis is
negative, then for example BaLaZTi4O12i
titanium dioxide and/or strontium titanate (SrTiO3) are used to make a
corrective adjustment of the glass ceramic
mass towards 0 ppm/K. However, if the Tf value of the glass ceramic mass
serving as the basis is positive, then
for example BaSmZTi4OiZ, aluminum oxide and lanthanum borate (LaBO3) can be
used to adjust the Tf value. The
additional oxides which are used for corrective adjustment can be added before
sintering of the glass ceramic mass
takes place. However, these oxides can also be the aforementioned
crystallization products.
The rare earth metal Reg is present for example as the trioxide RegZ03. By
using the oxide of the rare earth metal
Reg, it is possible match the permittivity of the glass material, which
contributes to the permittivity of the overall
glass ceramic mass, to the perrrrittivity of the oxide ceramic. A glass
ceramic mass exhibiting a permittivity of 15 to
80 or even higher is thus accessible.
In particular, the rare earth metal Rek and/or the rare earth metal Reg are
selected from the group comprising
lanthanum and/or neodymium and/or samarium. Other lanthanides or even
actinides are also conceivable. The rare
earth metals Rek and Reg can be identical, but can also be different rare
earth metals.
In a special embodiment, the tetravalent metal Me4+ is selected from the group
comprising silicon and/or
germanium and/or tin and/or titanium and/or zirconium and/or hafnium. In
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particular, the oxides from the subgroup elements titanium, zirconium and
hafnium themselves influence the
dielectric material properties of the glass ceramic mass. In particular, these
oxides influence the formation of the
crystallization products. The oxides of the main group elements silicon,
germanium and tin principally support a
glassiness of the glass niaterial. These oxides are used to control the
viscosity temperature characteristic of the glass
material.
In a special embodiment, the pentavalent metal Me5+ is selected from the group
comprising bismuth and/or
vanadium and/or niobium and/or tantalum. It also holds true here that oxides
from the subgroup elements vanadium,
niobium and tantalum (niobium pentoxide Nb205 or tantalum pentoxide Ta205 for
example) directly influence the
dielectric material properties. In particular, these oxides influence the
formation of the crystallization products and
thus indirectly the material properties. An oxide of bismuth as the main group
element primarily supports the
glassiness of the glass material.
In a further embodiment, the glass material contains at least one oxide with
at least one further metal Mex, which is
selected from the group comprising aluminum and/or magnesium and/or calcium
and/or strontium and/or barium
and/or copper and/or zinc. The further metal Mex can be present as a separate
oxidic phase. The glassiness of the
glass niaterial can be stabilized by using the oxides aluminum trioxide
(A1203), magnesium oxide (MgO), calcium
oxide (CaO), strontium oxide (SrO) and barium oxide (BaO).
In a special embodiment, in addition to barium as a bivalent metal the oxide
ceramic contains a doping of at least
one further bivalent metal Me2+. In particular, in this situation the further
bivalent metal Me2+ is selected from the
group comprising copper and/or zinc. For example, the
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oxide ceramic having the composition BaRek2Ti4O12 is doped with zinc. The
bivalent metal Me2+ controls the
dielectric material properties of the oxide ceramic. During sintering, in
particular during a further treatment of the
glass ceramic at higher temperatures, partial dissolution of the oxide
ceraniic in the glass melt can occur, with
subsequent crystallization. It has become apparent that it is particularly
advantageous if the glass material or an
oxide of the glass material is doped with the bivalent metal Me2+ which also
occurs in the oxide ceramic. The same
also applies to other crystalline additions in the glass material. An oxide of
an alkaline earth metal as a bivalent
metal Me2+ increases the basicity of the glass material and thus a reactivity
of the glass material with respect to a
basic oxide ceramic. The coniposition of the oxide ceramic is therefore
largely maintained during the compression
process. It has become apparent that it is particularly advantageous if the
oxide ceramic is doped with a bivalent
metal Me2+ which also occurs in the glass material. In particular, zinc is to
be mentioned here as a bivalent metal
Me2+.
In a special embodiment, 100% by volume of the glass ceramic mass is composed
of a ceramic proportion of the
oxide ceramic which is selected from the range between 20% by volume inclusive
to 60% by volume inclusive, and
a glass proportion of the glass material which is selected from the range
between 80% by volume inclusive to 40%
by volume inclusive. In particular, the ceramic proportion is selected from
the range between 30% by volume
inclusive to 50% by volume inclusive and the glass proportion is selected from
the range between 70% by volume
inclusive to 50% by volume inclusive. With regard to these compositions,
compression takes place primarily by
viscous flow.
In particular, the oxide ceramic and/or the glass material contain a powder
with a mean particle
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size (Dsa value) which is selected from the range between 0.8 m inclusive and
3.0 m inclusive. The mean particle
size is also referred to as half-value particle size. The oxide ceramic and
the glass material are each present as a
powder of such a type. The mean particle size in particular lies between 1.5
m and 2.0 m. It has become apparent
that with a particle size from the aforementioned range it is possible to
exercise good control over a possible
5 reactive eluation of individual constituents of the oxide ceramic or of
crystalline additions in the glass material.
Advantageously, the particle size does not exceed 3 m in order to allow
vitrification of the glass ceramic mass to
take place.
Normally, in order to reduce the sintering temperature and to increase the
permittivity of the glass ceramic mass,
lead oxide (PbO) is added to the glass niaterial. With regard to the present
invention, the lead oxide proportion
10 and/or cadniium oxide proportion of the glass ceramic mass and/or of the
oxide ceramic and/or of the glass material
is a maximum 0.1 %, in particular a maximum of I ppm. By preference, with
regard to environmental
considerations, the proportion of lead oxide and cadmium oxide is almost zero.
This is achieved by the present
invention without significant restriction of the material properties of the
glass ceramic mass.
In particular, the glass ceramic mass exhibits a maximum vitrification
temperature of 850 C, and in particular a
maximum of 800 C. In this situation, in particular, a glass ceramic mass is
accessible with a permittivity which is
selected from the range between 20 inclusive and 80 inclusive, a quality which
is selected from the range between
300 inclusive and 5000 inclusive, and a Tf value which is selected from the
range between - 20 ppm/K inclusive
and + 20 ppm/K inclusive. With these niaterial properties, the glass ceramic
mass is very well suited for use in
microwave technology.
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According to a second aspect of the invention, a
ceramic body using a previously described glass ceramic mass
is specified. In particular, the ceramic body has at least
one elementary metal MeO which is selected from the group
comprising gold and/or silver and/or copper. By preference,
the ceramic body is a ceramic multilayer body. The
previously described glass ceramic mass is used to
manufacture the ceramic body. In particular, a ceramic body
in the form of a ceramic multilayer body can be manufactured
in this manner. The glass ceramic mass is used in
particular in ceramic film blanks in LTCC technology. In
this way, glass ceramic masses are made available to the
LTCC technology, having excellent material properties for
the manufacture of microwave technology components. In
addition, the glass ceramic mass which sinters at a low
temperature can be used in order to suppress the lateral
shrinkage occurring during the manufacture of a ceramic
multilayer body.
According to another broad aspect, there is
provided glass ceramic mass comprising at least one oxide
ceramic, containing barium, titanium and at least one rare
earth metal Rek, and at least one glass material, containing
at least one oxide with boron and at least one oxide with at
least one tetravalent metal Me4+ selected from the group
consisting of titanium, zirconium, and hafnium, the glass
material containing at least one oxide with at least one
rare earth metal Reg, wherein the oxide ceramic is doped
with copper 2+.
According to another broad aspect, there is
provided glass ceramic mass comprising at least one oxide
ceramic, containing barium, titanium and at least one rare
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earth metal Rek, and at least one glass material, containing
at least one oxide with boron and at least one oxide with at
least one tetravalent metal Me4+ selected from the group
consisting of titanium, zirconium, and hafnium, the glass
material containing at least one oxide with at least one
rare earth metal Reg, wherein the oxide ceramic is doped
with zinc 2+.
According to another broad aspect, there is
provided glass ceramic mass comprising at least one oxide
ceramic, containing barium, titanium and at least one rare
earth metal Rek, and at least one glass material, containing
at least one oxide with boron and at least one oxide with at
least one tetravalent metal Me4+ selected from the group
consisting of titanium, zirconium, and hafnium, the glass
material containing at least one oxide with at least one
rare earth metal Reg, wherein the oxide ceramic is doped
with copper 2+ and zinc 2+.
According to another broad aspect, there is
provided glass ceramic mass comprising at least one oxide
ceramic, containing barium, titanium and at least one rare
earth metal Rek, and at least one glass material, containing
at least one oxide with boron and at least one oxide with at
least one pentavalent metal Me5+ selected from the group
consisting of vanadium, niobium, tantalum and at least one
oxide with at least one rare earth metal Reg, characterized
in that the oxide ceramic is doped with copper 2+.
According to another broad aspect, there is
provided glass ceramic mass comprising at least one oxide
ceramic, containing barium, titanium and at least one rare
earth metal Rek, and at least one glass material, containing
at least one oxide with boron and at least one oxide with at
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least one pentavalent metal Me5+ selected from the group
consisting of vanadium, niobium, tantalum and at least one
oxide with at least one rare earth metal Reg, characterized
in that the oxide ceramic is doped with zinc 2+.
According to another broad aspect, there is
provided glass ceramic mass comprising at least one oxide
ceramic, containing barium, titanium and at least one rare
earth metal Rek, and at least one glass material, containing
at least one oxide with boron and at least one oxide with at
least one pentavalent metal MeS+ selected from the group
consisting of vanadium, niobium, tantalum and at least one
oxide with at least one rare earth metal Reg, characterized
in that the oxide ceramic is doped with copper 2+ and zinc
2+.
According to another broad aspect, there is
provided a use of the glass ceramic mass summarized above to
produce a ceramic body having at least one elementary metal
MeO which is selected from the group consisting of gold,
silver, and copper.
To summarize, the following advantages result from
the invention:
= The composition of the glass ceramic mass using
oxide ceramic and glass material is selected such that
compression takes place primarily by viscous flow and
crystallization products are formed during and/or after
compression.
= The composition of the oxide ceramic remains
essentially constant during sintering of the glass ceramic
mass. The material properties of the glass ceramic mass can
thus be very well predetermined.
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= By means of suitable (oxidic) additions to the
oxide ceramic and to the glass material, the sintering
behavior of the glass ceramic mass and the material
properties of the glass ceramic
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mass can be set ahnost as desired. It is thus possible, for example, to set
permittivity, quality and Tf value over
a wide range whilst retaining a low vitrification teniperature.
= Almost complete compression (vitrification) of the glass ceramic mass can be
achieved below 850 C, as a
result of which the ceramic mass is suitable for use in LTCC technology. In
combination with glass ceramic
mass in particular, which compresses at a higher temperature, a lateral
shrinkage of below 2% can be achieved
in a multistage sintering process.
= Compression is achieved without the use of lead oxide and/or cadniium oxide.
The invention will be described in the following with reference to an
embodiment and the associated drawing. The
drawing shows a schematic cross-section, not to scale, of a ceranmic body with
the glass ceramic mass in a
multilayer construction.
According to the embodiment, the glass ceraniic mass 11 is a powder consisting
of an oxide ceramic and a powder
of a glass material. The oxide ceramic has the formal composition
BaRek2Ti4O12. The rare earth metal is
neodymium. The oxide ceramic is doped with a bivalent metal Me2+ in the form
of zinc. In order to manufacture
the oxide ceramic, appropriate quantities of barium oxide, titanium dioxide
and neodymium trioxide are mixed
together with approximately one % by weight zinc oxide, calcinated or
sintered, and subsequently ground to
produce the corresponding powder.
The glass material has the following composition: 35.0 % mol% boron trioxide,
23.0 mol% lanthanum trioxide and
42 mol% titanium dioxide. Moreover, alkaline earth metal oxides and
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zirconium dioxide at below 5% by weight are mixed with the glass material,
whereby the ratio between boron
trioxide and the sum of the oxides of the tetravalent metals titanium and
zirconium is approximately 0.75.
100% by volume of the glass ceramic mass is composed of 35% by volume of the
ceramic material and 65% by
volume of the glass material. Ceramic material and glass material have a D50
value of 1.0 m. The vitrification
temperature of the glass ceramic mass is 760 C.
During firing of the glass ceramic mass at a certain firing temperature the
glass ceramic mass compresses. In
addition, the crystallization product titanium dioxide is formed, which acts
as a component serving to set the Tf
value. Crystalline ritanium dioxide at 15% by weight is obtained.
Depending on the firing temperature of the ceramic mass, the following
dielectric material properties are set for the
glass ceramic mass (at 6 GHz):
At a firing temperature of 790 C the result is a permittivity of 34, a quality
of 400 and a Tf value of -163 ppm/K.
At a firing temperature of 820 C the result is a permittivity of 32, a quality
of over 1000 and a Tf value of -4 ppm.
A firing regime which results in the specified values consists in a first
heating phase having a heating rate of 2
K/min to a temperature of 500 C, a first dwell time of the temperature of 30
minutes, a second heating phase having
a heating rate of 10 K/min, a second dwell time of 5 K/min and a cooling phase
of 5 K/min to room temperature.
The glass ceramic mass 11 described is used in order to integrate a passive
electrical component 6, 7 in the volume
of a ceramic multilayer body 1 with the aid of LTCC technology. The passive
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electrical component 6, 7 consists of the elementary metal MeO silver. In
order to produce the multilayer body 1, a
composite is produced from ceramic film blanks with the glass ceramic mass 11
and Heratape film blanks with
the ceramic mass 12 which is different from the glass ceramic mass 12. The
ceramic layers 3 and 4 of the ceramic
multilayer body 1 are created from the ceramic film blanks together with the
glass ceramic mass 11 as a result of the
sintering process. The ceramic layers 2 and 5 result from the Heratape film
blanks. In the composite, at a firing
temperature of 860 C (vitrification temperature of the Heratape film blanks)
a permittivity of 30, a quality of over
1000 and a Tf value of + 8 ppm/K are achieved for the glass ceramic mass. At a
firing temperature of 900 C a
perniittivity of 28, a quality of over 1000 and a Tf value of + 142 are
obtained.
